Biophysics最新文献

In order to further clarify the mechanisms of pharmacological effects of salicylic and acetylsalicylic acids, the interactions of these acids with mitochondrial and erythrocyte membranes were studied and the role of calcium ions/protons in the effects of salicylates was evaluated. Salicylic acid and, to a lesser extent, acetylsalicylic acid at concentrations of 0.5–2.0 mM effectively inhibited the respiratory activity of isolated rat liver mitochondria by uncoupling respiration and phosphorylation processes, induced depolarization of the mitochondrial membrane and potentiated Ca²⁺-stimulated formation of mitochondrial permeability transition pore in EGTA-free media. Cyclosporine A and ruthenium red partially inhibited the mitochondrial pore opening process induced by salicylic and acetylsalicylic acids both in the absence and in the presence of Ca²⁺ ions. Salicylic acid (180–360 μM) significantly accelerated proton-induced lysis (at pH 3.2) of human erythrocytes and caused hyperpolarization of erythrocyte membranes (at pH 5.5, but not at pH 7.4), probably as a result of proton transfer into the cytoplasm of the cell. Thus, salicylic and acetylsalicylic acids interact with mitochondrial and plasma membranes, act as effective proton/Ca²⁺ ionophores, and stimulate the mitochondrial calcium uniporter.

The formation of behavioral skills, consisting of the ability to learn the conditioned reaction of active avoidance, in different lines of rats in a three-way maze has been experimentally studied. To determine the most trained lines, white mongrel rats (100 individuals) and Long Evans and Dumbo rats (30 individuals each) were selected. The conditional stimulus was a combination of turning on a sound and turning off a light in a randomly selected target corridor of the maze. At 5 s after turning on the sound, the light was turned off, an unconditional stimulus (electric current) was supplied to the nontarget corridors and the light was turned on. The task of the rat was to make the transition to the target (safe) way of the maze in response to a sound stimulus. Upon reaching the target, the voltage was removed from the floor of the nontarget corridors and the lights were turned off. The pause between the combinations of conditional/unconditional stimulus was 30 s, the training time for each type of rat was 1 month with 20 presentations of combinations of stimuli per day. Each rat was considered trained with a probability of achieving the goal in 70% or more cases in a time not exceeding 6 s. It has been found that Dumbo rats were best suited for rapid training of large groups of rats to respond to an irritating stimulus.

The effects of uridine and its monophosphoryl derivative on the level of the main biochemical markers of myocardial damage in the blood and on the electrical activity of the heart were investigated in a rat model of cardiomyopathy induced by isoprenaline. It was shown that administration of isoprenaline (150 mg/kg, subcutaneously) caused an increase in the activity of serum enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT), leading to an elevated AST/ALT ratio (De Ritis ratio), and enhanced activity of lactate dehydrogenase in blood lymphocytes, which confirms the development of myocardial damage in experimental animals. ECG analysis revealed prolongation of the RR, P-R, QT, and QTc intervals and the QRS complex, indicating that the duration of both depolarization and repolarization phases increased relative to the duration of the cardiac cycle in rats with isoprenaline-induced myocardial damage. Preliminary administration of uridine and uridine-5'-monophosphate to experimental animals at a dose of 30 mg/kg equally effectively prevented an increase in the enzymatic activity of AST and the De Ritis ratio, led to a decrease in the duration of P-R, QRS, QT, and QTc intervals, and partially normalized the metabolic activity of rat blood lymphocytes. These findings suggest that uridine and uridine-5'-monophosphate have a similar protective effect on the contractile function of cardiomyocytes and can be considered as agents for metabolic therapy in the treatment of ischemic heart disease.

This review is devoted to modern concepts of paraptosis as one of the types of regulated cell death, in comparison with other types of cell death. Paraptosis is a form of cell death caused by stress of the endoplasmic reticulum (ER), accompanied by the accumulation of damaged or incorrectly folded proteins in it, extensive nonautophagic vacuolation of the cisterns of the endoplasmic reticulum and, in some cases, mitochondria, with subsequent damage to the mitochondria and cytoskeleton and cell death. Knowledge about the molecular mechanisms of paraptosis is of interest for the treatment of cancer diseases resistant to apoptosis-inducing agents.

The existing concepts of the molecular mechanisms of pathological hyperexcitability and synchronization of neural networks in epileptogenesis, including potassium, GABA, membrane (cellular) and synaptic (network) models, are discussed. The focus of such models is the imbalance between excitation and inhibition involving numerous positive and negative feedback loops in neural networks. The paper considers modern concepts of (1) the reliability of dynamic systems with a large number of negative feedback loops and (2) the degeneracy, that is, the ability of heterogeneous elements (channels and currents) to replace each other, as the basis for the stable functioning of hyperexcitable networks in channelopathy and hyperexpression of various channels. The paper suggests a possible mechanism for the spontaneous occurrence of convulsive activity and accumulation of potassium in the intercellular space, based on the activation of a group of cationic channels (HCN, K_ir2.x , hERG, Na_v1.х, and BK_Ca), which provides reliability and high sensitivity of epileptiform activity to external and internal factors due to degeneracy and formation of a group of connections of positive feedback loops.

The use of ionizing radiation at an ultra-high dose rate (≥40 Gy/s), which is called FLASH irradiation, contributes to the preservation of healthy tissues with a level of tumor control comparable to that of irradiation at a standard dose rate. This review summarizes the current knowledge obtained in studies of irradiation of tumor and normal cell lines and animals, including tumor carriers, in conventional and FLASH modes. For comparison, data on FLASH irradiation with photons, electrons, and protons, as well as ions of helium and carbon, are also provided. The biophysical, molecular biological, and immunological aspects of FLASH exposure necessary for understanding radiation-induced processes in cells and tissues in order to improve tumor radiotherapy are discussed.

The effect of high-energy (660 MeV) proton irradiation at the phasotron accelerator in FLASH mode (80 Gy/s) compared with the standard proton exposure power of 3.0 Gy/min was studied. When irradiated in two modes at doses of 1.0 and 1.5 Gy, the induction of cytogenetic damage in bone marrow cells and the state of lymphoid organs (thymus and spleen) were evaluated; survival under total in vivo irradiation of mice was analyzed at doses of 7.0 and 8.0 Gy. The growth rate of a model tumor under ex vivo irradiation was determined at doses of 40 and 60 Gy. It has been shown that irradiation of animals in the FLASH mode at a dose of 1.5 Gy protected the proliferative activity of the spleen and also led to a decrease in cytogenetic damage in bone marrow erythrocytes according to the micronucleus test compared with the standard irradiation mode at a dose of 1.5 Gy, that is, a milder effect of the FLASH mode dose was observed. However, irradiation of mice in FLASH mode at high doses (7.0 and 8.0 Gy) led to earlier death of animals compared to the standard irradiation regime. A tumor node formed with further growth only after FLASH irradiation of a suspension of Ehrlich ascites carcinoma at a dose of 40 Gy; in all other groups a tumor was not formed.

The mitochondrial inhibitors rotenone and rhodamine 123 and the Janus Green B dye are being studied in order to develop pharmacological agents that cause mitochondrial dysfunction and apoptosis. Since mitochondrial dysfunction is associated with the production of reactive oxygen species, it seems relevant to compare the DNA damage induced by these substances to cells of ascitic Ehrlich carcinoma and murine lymphocytic leukemia P388 with exposure to a known inducer of reactive oxygen species, that is, ionizing (X-ray) radiation. The level of DNA damage was assessed using an alkaline version of the Comet assay. The level of DNA damage induced by rotenone was comparable to irradiation at a dose of 4 Gy in both cell types. Post-radiation incubation reduced the level of DNA damage, which indicates DNA repair. Treatment of Ehrlich’s ascitic carcinoma cells with rhodamine 123 followed by washing did not cause this increase; however, irradiation at a dose of 4 Gy in the presence of rhodamine 123 induced an increase in the level of DNA damage, which significantly decreased after 1 h incubation. It can be assumed that pretreatment of cells with rotenone and rhodamine 123, which impair the work of mitochondria, contributed to the preservation of the integrity of nuclear DNA in irradiated cells. Exposure to Janus Green B caused increased DNA damage and cell death. Based on the alkaline version of the Comet assay, damage induced by these compounds can be considered as single- and double-strand breaks and alkali-labile (apurine/apirimidine) sites in DNA.

A method of extraction of quercetin from a plant cell based on the combined action of ultrasound and a metastable fraction of an aqueous solution is proposed. This treatment leads to more efficient release of the cytoplasmic component due to etching and/or mechanical destruction of the plant cell envelope. The oxidized fraction of the solution has the most pronounced extractive properties; however, it acts on quercetin by oxidizing the chromophore part of the molecule. According to the criterion of pigment preservation, the best extraction medium is the reduced fraction of water. Analytical methods were used to analyze the extract samples: UV-Vis spectroscopy, gel electrophoresis of proteins, ¹H NMR spectroscopy, and QCM weighing, as well as scanning electron microscopy.